JP4734298B2 - Lithographic apparatus and device manufacturing method - Google Patents

Description

The present invention relates to a control system for controlling a position parameter of a stage in a lithographic apparatus, a lithographic apparatus including such a control system, and a device manufacturing method.

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, typically the target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that case, a patterning device, also referred to as a mask or reticle, is used to generate circuit patterns to be formed on individual layers of the IC. This pattern can be transferred onto a target portion (eg, partially containing one or more dies) on a substrate (eg, a silicon wafer). Pattern transfer is typically performed via imaging onto a layer of radiation sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. A conventional lithographic apparatus scans a pattern in a given direction ("scan" direction) with a radiation beam, and a so-called stepper that irradiates each of the target portions by exposing the entire pattern to the target portion at once. There are so-called scanners in which each of the target portions is illuminated by synchronously scanning the substrate parallel to this direction or non-parallel. It is also possible to transfer the pattern from the patterning device to the substrate by transferring the pattern to the substrate.

The lithographic apparatus includes a substrate table for supporting the substrate. The substrate table is positioned under the control of a control system capable of positioning a target portion of the substrate substantially within the focal plane of the projection system of the lithographic apparatus. Thus, the control system operates in a coordinate system related to the position of the projection system or the position of the image formed by the projection system on the substrate. The substrate table position measurement system can be configured to perform position measurement of the substrate table with respect to the origin of such a coordinate system. Typically, this origin is provided at the height of the substrate just below the center of the lens. The position of the substrate table is controlled using a plurality of controllers, each functioning in one of the coordinates measured by the measurement system. For example, there may be a controller that operates in X, Y, Z, Rx, Ry, Rz coordinates. The latter three represent rotations about the X, Y and Z axes, respectively. Thus, each of these controllers has a controller force or torque (ie, a controller output signal to drive the actuator) as responsive to a deviation from the corresponding position set point of the actual measurement position in its coordinate system. The actuator thereby generates a force or torque). The force and torque thus calculated by the controller are also determined in the coordinate system as defined above in relation to the lens center.

However, the position of the center of gravity of the substrate table may not coincide with the origin of this coordinate system. In particular, the position of the center of gravity of the substrate table moves as the position of the substrate table changes with respect to the coordinate system. Here, for example, when the Rx controller generates torque for accelerating the substrate table around the X axis in response to the movement of the center of gravity of the substrate table relative to the origin of the coordinate system in the Y direction, Z acceleration occurs, and as a result, Z A position error occurs. This is caused by the fact that the torque in the Rx direction on the stage tilts the stage around a line that intersects the center of gravity of the stage, rather than around the origin of the coordinate system under the lens, as desired. The resulting Z direction error causes the Z controller to react and reduce this error to zero, but at this point a Z error has already occurred, which is undesirable.

In order to correct this influence, a conversion matrix called a gain scheduling matrix is used. This matrix converts the force and torque generated by the controller in the coordinate system associated with the lens to the force and torque in the substrate table coordinate system defined by the position of its center of gravity. In the above example, when the Rx controller generates the torque for accelerating the substrate table around the X axis according to the position of the substrate table in the Y direction, as described above, it will occur in the Z direction that will not occur if it is not corrected. An additional force in the Z direction that corrects the error is generated. Then, instead of tilting around a line extending in the X direction across the stage's center of gravity, the gain scheduling matrix is determined by the above coordinate system so that the substrate is in the focal plane of the lens and hence the table is associated with the lens. Generate an additional force in the Z direction that ensures that it actually tilts around a defined X axis. The additional force generated in the Z direction is proportional to the torque generated by the controller around the X axis, the origin of the coordinate system in the Y direction, and the distance of the stage centroid relative to the stage mass, and inversely proportional to the inertia of the stage around the X axis. .

[0006] Similar techniques are applied to the torque around the Y and Z axes that affect the X, Y and Z position errors. The gain scheduling matrix ensures that the controller forces and torques in the coordinate system associated with the lens are translated into forces and torques in the coordinate system associated with the center of gravity of the substrate table. These forces and torques are then applied to the substrate table using an actuator that is necessarily coupled to a fixed location relative to the center of gravity of the substrate table.

However, the disturbance force and disturbance torque do not necessarily follow the gain scheduling compensation used for the force and torque generated by the controller, and thus act directly on the stage. As a result, the disturbance torque affects the other direction. As an example, when the stage is positioned off-center, disturbance torque that tends to tilt the stage relative to an axis extending through the center of gravity of the stage along the focal plane of the projection system can cause the stage to tilt. Will cause an error in the vertical position of the target portion under the lens center. Here, the term vertical is understood to be a direction perpendicular to the focal plane. As a result, the disturbance torque may cause a focus error, and hence degradation of the accuracy of the pattern projected on the substrate. If this torque does not act on the stage as a disturbance torque, but is generated by the controller as a signal to generate such torque, a gain scheduling matrix is used to compensate for the effects of the vertical displacement described above. Note that can apply a vertical force. Therefore, the gain scheduling matrix can effectively suppress the influence when the influence is caused by the torque from the controller, but cannot suppress the influence when the influence is a disturbance torque.

[0008] It would be desirable to provide an improved control system for a lithographic apparatus and a lithographic apparatus comprising such a control system.

[0009] According to an embodiment of the present invention, a control system is provided for controlling a position parameter of a stage in a lithographic apparatus, the control system comprising: a stage controller for controlling a position parameter of the stage in at least a first direction; A disturbance torque estimator for estimating a disturbance torque on the stage around an axis extending in a second direction substantially perpendicular to the first direction, and substantially for the estimated disturbance torque and the first and second directions; A signal representative of the position of the stage in a third direction that is generally orthogonal is provided to determine a feed forward correction signal for correcting a position error of the stage in the first direction due to disturbance torque, A correction signal calculator for supplying a forward correction signal to the stage.

[0010] In another embodiment of the invention, there is provided a lithographic apparatus for transferring a pattern on a substrate, the lithographic apparatus comprising: a stage for holding a substrate; and a position of the stage for controlling the position of the stage. A control system according to the above embodiment.

[0011] According to a further embodiment of the present invention, a step of irradiating a pattern onto a substrate by the lithographic apparatus of one embodiment of the present invention, a step of developing the irradiated substrate, and from the developed substrate There is provided a device manufacturing method including a device manufacturing process.

[0012] In one embodiment of the present invention, an illumination system configured to condition a radiation beam and a patterning device configured to pattern the radiation beam to form a patterned radiation beam are supported. A patterning device support configured to support the substrate, a substrate support configured to support the substrate, a projection system configured to project the patterned beam of radiation onto the substrate, and at least a first A stage controller configured to control one positional parameter of the directional support, a disturbance torque on one of the supports around an axis extending in a second direction substantially orthogonal to the first direction And a third direction substantially orthogonal to the estimated disturbance torque and the first and second directions. And a signal representative of a position of one support and configured to determine a feedforward correction signal for correcting one position error of the support in a first direction due to disturbance torque. There is provided a lithographic apparatus comprising: a control system configured to control one positional parameter of the support, comprising a correction signal calculator, wherein the feedforward correction signal is supplied to one of the supports. The

[0013] In yet another embodiment of the invention, the radiation beam is adjusted to form a patterned radiation beam using the patterning device supported by the patterning device support and the patterning device support. , Projecting the patterned beam of radiation onto a substrate supported by the substrate support, and controlling at least one positional parameter of the support in the first direction. A stage torque controller, a disturbance torque estimator configured to estimate a disturbance torque on one of the supports around an axis extending in a second direction substantially perpendicular to the first direction, and the estimation A disturbance torque and a signal representative of the position of one of the supports in a third direction substantially orthogonal to the first and second directions. And configured to determine a feedforward correction signal for correcting one position error of the support in the first direction due to disturbance torque, and the feedforward correction signal is supplied to one of the supports. Using a control system with a correction signal calculator to control one positional parameter of the support.

[0014] Embodiments of the present invention are described below with reference to the accompanying schematic drawings, which are merely examples. In the figure, corresponding reference symbols indicate corresponding parts.

[0020] Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The lithographic apparatus supports an illumination system (illuminator) IL configured to condition a radiation beam B (eg UV radiation or any other suitable radiation), and a patterning device (eg mask) MA, And a mask support structure (eg, mask table) MT connected to a first positioner PM configured to accurately position the patterning device according to certain parameters. The lithographic apparatus is further connected to a second positioner PW configured to accurately position the substrate according to certain parameters configured to hold a substrate (eg, resist coated wafer) W. A substrate table (e.g. wafer table) WT or "substrate support". The lithographic apparatus can further include a projection system (eg, a projection system) configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (eg, including one or more dies) of the substrate W. Refractive projection lens system) PS.

[0021] An illumination system is a refractive optical component, reflective optical component, magneto-optical component, electromagnetic optical component, electrostatic optical component or other type of optical component for directing, shaping or controlling radiation, or any of them Various types of optical components, such as any combination, can be provided.

[0022] The mask support structure supports the patterning device. That is, the mask support structure supports the weight of the patterning device. The mask support structure holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The mask support structure can use mechanical clamping techniques, vacuum clamping techniques, electrostatic clamping techniques or other clamping techniques to hold the patterning device. The mask support structure may be, for example, a frame that can be fixed or moved as required, or a table. The mask support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device”.

[0023] As used herein, the term "patterning device" refers to any device that can be used to impart a pattern to a cross-section of a radiation beam and thereby generate a pattern on a target portion of a substrate. It should be interpreted broadly as meaning. It should be noted that the pattern imparted to the radiation beam may not necessarily correspond exactly to the desired pattern in the target portion of the substrate, for example if the pattern comprises a phase shift feature or so-called assist feature. . The pattern imparted to the radiation beam typically corresponds to a particular functional layer in a device such as an integrated circuit, which is generated in the target portion.

[0024] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift and attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array uses micromirrors arranged in a matrix. Each of the micromirrors can be individually tilted so that the incident radiation beam reflects in different directions. This tilted mirror gives a pattern to the radiation beam reflected by the mirror matrix.

[0025] As used herein, the term "projection system" includes refractive optics that are suitable for the exposure radiation used or suitable for other factors such as the use of immersion liquid or the use of a vacuum. Broadly defined to encompass any type of projection system, including systems, reflective optical systems, catadioptric optical systems, magneto-optical systems, electromagnetic optical systems and electrostatic optical systems, or any combination thereof I want to be interpreted. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

[0026] As shown, the device is a transmissive (eg, using a transmissive mask) type device. Alternatively, the device may be of a reflective type (for example using a programmable mirror array of the type referenced above or using a reflective mask).

[0027] The lithographic apparatus is an apparatus of a type optionally having two (dual stage) or more substrate tables or "substrate supports" (and / or two or more mask tables or "mask supports"). In such "multi-stage" machines, an additional table or support can be used in parallel, or while one or more other tables or supports are being used for exposure. Preliminary steps can be performed on one or more tables or supports.

[0028] The lithographic apparatus may also be of a type in which at least a portion of the substrate is covered with a liquid having a relatively high refractive index, for example water, thereby filling a space between the projection system and the substrate. Good. It is also possible to apply immersion liquid to other spaces in the lithographic apparatus, for example, between the mask and the projection system. An immersion technique can be used to increase the numerical aperture of the projection system. As used herein, the term “immersion” does not imply that a structure, such as a substrate, must be submerged in a liquid, but simply during the exposure between the projection system and the substrate. It only means that liquid is placed between them.

Referring to FIG. 1, the illuminator IL receives a radiation beam from a radiation source SO. If the radiation source is, for example, an excimer laser, the radiation source and the lithographic apparatus can be separate components. In that case, the radiation source is not considered to form part of the lithographic apparatus, and the radiation beam is emitted using, for example, a beam delivery system BD equipped with a suitable guiding mirror and / or beam expander. Delivered from SO to illuminator IL. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The radiation source SO and the illuminator IL can be referred to as a radiation system together with a beam delivery system BD, if desired.

[0030] The illuminator IL may comprise an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. In general, at least the outer and / or inner radius ranges (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the pupil plane of the illuminator can be adjusted. The illuminator IL may also include various other components such as an integrator IN and a capacitor CO. An illuminator can be used to adjust the radiation beam to give the desired uniform intensity distribution to its cross section.

[0031] The radiation beam B is incident on the patterning device (eg, mask MA), which is held on the mask support structure (eg, mask table MT), and is patterned by the patterning device. The radiation beam B transmitted through the mask MA passes through a projection system PS that focuses the radiation beam onto a target portion C of the substrate W. The substrate table WT can be accurately moved using a second positioner PW and a position sensor IF (eg interferometer device, linear encoder or capacitive sensor), so that for example different target portions C of the radiation beam B It can be positioned in the optical path. Similarly, using the first positioner PM and another position sensor (not explicitly shown in FIG. 1), for example after mechanical retrieval from a mask library or during a scan, the mask MA It can be accurately positioned with respect to the optical path of the radiation beam B. Usually, the movement of the mask table MT is realized by using a long stroke module (coarse positioning) and a short stroke module (fine movement positioning) which form a part of the first positioner PM. Similarly, movement of the substrate table WT or “substrate support” is realized using a long stroke module and a short stroke module forming part of the second positioner PW. In the case of a stepper (not a scanner), the mask table MT can be connected only to a short stroke actuator or can be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although a substrate alignment mark occupying a dedicated target portion is illustrated, the substrate alignment mark can also be placed in the space between the target portion (such a substrate alignment mark is Known as the scribe lane alignment mark). Similarly, if multiple dies are provided on the mask MA, a mask alignment mark can be placed between the dies.

[0032] The apparatus shown in the figure can be used in at least one of the following modes.

[0033] In the step mode, the mask table MT or “mask support” and the substrate table WT or “substrate support” are basically kept stationary so that the entire pattern imparted to the radiation beam is applied once to the target portion C. Projected (ie, a single static exposure). Next, the substrate table WT or “substrate support” is shifted in the X and / or Y direction and a different target portion C is exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

[0034] 2. In scan mode, the mask table MT or “mask support” and the substrate table WT or “substrate support” are scanned synchronously while the pattern imparted to the radiation beam is projected onto the target portion C (see FIG. Ie single dynamic exposure). The speed and direction of the substrate table WT or “substrate support” relative to the mask table MT or “mask support” depends on the magnification (reduction ratio) and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width of the target portion in single dynamic exposure (width in the non-scan direction), while the length of the scan motion (height in the scan direction). ) Is decided.

[0035] 3. In another mode, the mask table MT or “mask support” is held essentially stationary to hold the programmable patterning device, while the pattern imparted to the radiation beam is projected onto the target portion C. The substrate table WT or “substrate support” is moved or scanned. In this mode, a pulsed radiation source is typically used and programmable patterning is performed as needed during each scan of the substrate table WT or “substrate support” or between successive radiation pulses. The device is updated. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0036] Combinations and / or variations on the above usage modes or entirely different usage modes may also be used.

FIG. 2 shows a control diagram of a control system for controlling the position of the stage P of the lithographic apparatus. The control system includes three closed loop control loops that are Rx, Ry and Z control loops, thereby controlling rotation about an axis extending in the X and Y directions and position in the Z direction. In the context of this specification, the directions X and Y define a plane that is substantially parallel to the focal plane of the projection system, while the Z direction is substantially orthogonal to the focal plane, and thus the projection. Note that it is understood to be substantially parallel to the optical axis of the system. Each of these control loops includes the set points Rx, Ry and Z shown on the left side of FIG. 2, the controller (Rx controller, Ry controller and Z controller), and in this example the output of process P representing the stage and its actuator. To the subtraction point from which the feedback signal is subtracted from the set point signal and its output provided to the individual controllers. In addition, FIG. 2 shows a gain scheduling matrix GS that provides X, Y position dependent compensation of the controller output (eg, controller signal representing force). The reason for providing the gain scheduling has already been described above in connection with the background art. In some embodiments of the present invention, the gain scheduling matrix included in the exemplary embodiment in the Rx, Ry and Z feedback loops may be omitted. In that case, the torque generated by the controller is not passed through the gain scheduling matrix, as described above, to avoid position errors. A disturbance torque estimator is provided to specify the disturbance torque Fd_est as shown in FIG. In this example, the estimated disturbance torque is around the axis extending in the X direction, and hence Rx disturbance torque. As a result of such disturbance torque, the stage tilts around its center of gravity, and as a result, when the center of gravity of the substrate table is not positioned below the lens center, the tilt around the axis extending in the X direction is the target portion. Will cause a Z position displacement of the stage, so that a stage position dependent focus error will occur. The farther the target portion of the substrate is from the center of gravity of the stage, the greater the influence of disturbance torque on the Z-direction position. If no further measures are taken as in the background art, this position-dependent error in the Z direction will be adjusted out by the feedback loop for the Z direction, It takes some time to correct this disturbance.

[0038] According to an embodiment of the present invention, there is provided a correction signal calculator denoted GS 'in FIG. 2, which includes an estimated disturbance torque, as will be described in more detail below. Also provided are the position of the stage in the Y direction, and in some cases the position of the stage in the X direction. The correction signal calculator determines a feed forward correction signal provided to the Z actuator input of stage P. A control system such as the one described here can also control the rest of the three degrees of freedom of the stage, for example the position in the X and Y directions and the rotation around the axis extending in the Z direction, Note that the control loop for degrees of freedom is omitted. Therefore, the control system of an embodiment of the present invention provides a stage controller (in this example because of the Z direction) for controlling the stage position parameter (in this example, the position) in the first direction (in this example, the Z direction). Controller), a disturbance torque estimator for estimating the disturbance torque Fd_est around the axis extending in the second direction (X direction in this example), the estimated disturbance torque and the third direction (Y direction in this example) And a signal representative of the position of the stage in the first direction are determined, and a feedforward correction signal for correcting the position error of the stage in the first direction caused by the disturbance torque Fdist is determined. Supplied to the stage (ie, added to the output signal of the controller in the Z direction (or a gain scheduling matrix is also provided). In this example that is, this is added to the gain scheduling matrix of the output signal), thus being supplied to the Z input of the stage P including its actuators, and a correction signal calculator GS '.

In FIG. 2, the disturbance torque estimator and the correction signal calculator are shown in relation to disturbance torque around an axis extending in the X direction. In order to be able to correct both the X-direction disturbance torque and the Y-direction disturbance torque, it may be similar to the estimator shown here, but connected to the corresponding signal of the Ry control loop instead of the Rx control loop. A second estimator may be provided. Thus, an estimated disturbance torque around an axis extending in the Y direction can be provided to the corresponding Ry input of the correction signal calculator GS '. Similarly, disturbance torque around an axis extending in the Z direction can be estimated by a third estimator and a corresponding X and / or Y position feedforward correction signal is determined.

An embodiment of the correction signal calculator GS ′ is schematically shown in FIG. FIG. 3 shows inputs for the position of the stage in the X and Y directions, inputs for forces on the stage in the X, Y and Z directions as indicated by F _x , F _y , F _z , and T _rx Fig. 6 shows a plurality of inputs including inputs for torque on the stage around an axis extending in the X, Y and Z dimensions respectively indicated by T _ry and T _rz . In addition, the correction signal calculator includes corresponding outputs for forces in the X, Y and Z directions and torque around the X, Y and Z axes. In the example shown here, in practice, four correction signals, each provided by an individual one of the blocks of this drawing, are calculated. However, for the example shown in FIG. 2, only one of the correction signals is used. In this example, only the correction signal determined by the torque around the axis extending in the X direction is used. That is, the estimated disturbance torque of FIG. 2 is therefore provided to the input _TRX of FIG. Also, for the determination of the correction signal, the position of the Y direction is used, as seen in FIG. 3, is determined correction signal in Z direction is added to the Z direction of the force F _Z. Therefore, the correction signal calculator is proportional to the estimated torque around the axis extending in the second direction (F _{X in} this example) and proportional to the position in the third direction (here, the position in the Y direction). Determine a feedforward correction signal (F _{Z in} this example) that is proportional to the mass of the stage as shown in m and inversely proportional to the inertia of the stage shown as J _X with respect to the second direction. To do. Therefore, this provides a correction that properly corrects the vertical error due to disturbance torque by a simple calculation. That is, the greater the torque, the greater the focus error, and the further away the stage from its center position where the center of gravity of the stage coincides with the optical axis of the projection system PS, the greater the error, so the correction signal must be further increased. In this embodiment, this correction signal is primarily dependent on the torque and position of the stage in the Y direction. The influence of stage mass and stage inertia is also taken into account.

As described above, it is also possible to add the second disturbance torque estimator and determine the disturbance torque around the axis extending in the Y direction. Such estimated disturbance torque is provided to the input TR _Ry of the correction signal calculator, which adds to the Z-direction force F _z while taking into account the X-direction position provided at the corresponding input X. The additional correction signal to be determined is then determined, and this F _z can then be provided to the corresponding input of the stage and actuator shown at P in FIG. Thus, in this way, two correction signals are determined by the individual equations and then added to form a correction signal in the Z direction. By taking into account the position in the X and Y directions, this correction is made to the distance between the lens center (ie, the optical axis), the position that is controlled when the focus and focal plane are related, and the stage position. It is assumed to depend. Therefore, in the above, the positions X and Y are presumed to represent the distances in the individual directions between the lens center and the stage position (determined by the position of its center of gravity in this example).

The matrix shown in FIG. 3 can be used not only as the correction signal calculator GS ′ but also as the gain scheduling matrix GS. Thereby, the correction signal calculator includes a copy of the gain scheduling matrix GS. However, the F _x , F _y and F _z inputs and the T _Rx , T _Ry and T _Rz outputs of the correction signal calculator GS ′ need not be connected. On the one hand, here the correction signal calculator can form a copy of the gain scheduling matrix, so using a copy of the gain scheduling matrix makes the implementation relatively simple, on the other hand, the disturbance torque is reduced to the controllers Rx and Ry, etc. This can provide a well-operated control system since it is treated in this way in the same way as the torque provided by the individual controllers. Note that the gain scheduling matrix can take into account the further relationship between position and torque, but for the sake of clarity, the dependency on the position in the Z direction is excluded from the embodiment shown in FIG. . If the T _Rx , T _Ry and T _Rz inputs as well as the F _x , F _y and F _z outputs (also the x and y position inputs) of the correction signal calculator GS ′ are utilized, a total of six corrections are included in this matrix. In the matrix, for each correction, the feedforward in the first direction is determined based on the disturbance torque around the axis extending in the second direction and the position of the stage in the third direction. The first, second and third directions are substantially perpendicular to each other. Since movement of the substrate table occurs substantially only in the X and Y planes, the Z position input may be omitted, but such input can be easily added to the exemplary embodiment of FIG. 3 by those skilled in the art. Please note that.

[0043] In the embodiment shown in FIG. 2, the controller includes a feedback controller, but those skilled in the art can apply the principles of the disturbance torque estimator and the correction signal calculator to any controller. It will be understood. However, in the feedback controller, the disturbance torque may be estimated in a practical or accurate manner. This is because the disturbance torque indicated by Fdist in FIG. 2 results in an error signal at the input of the Rx controller and a corresponding change in the output of this controller for driving the stage P. In general, in a closed loop negative feedback system that includes a controller C and a process P, the disturbance torque F _d is related to the output Y of the process P according to the following equation:
Y / F _d = P / (1 + PC)
Assuming here that the set point is 0, the error signal e is equal to the negative output signal Y, which can be rewritten as:
F _d = −P ⁻¹ e−Ce
Therefore, the disturbance torque can be expressed as a function of the error signal present at the input of each controller and the error signal present at the output of each controller multiplied by the transfer function of the controller. Such a function is illustrated in FIG. 2, which provides an error signal, ie a path from the input of the controller Rx to the summing device. In addition to the transfer function P ⁻¹ / N, this path also has a path from the output of the Rx controller having the transfer function 1 / N to the summing device. In the summing device, the outputs of the two paths are summed and multiplied by −1 to take into account the negative sign of the above equation, thereby obtaining an estimated disturbance torque. For practical reasons, a low pass filter is added to these equations. This is because the process transfer function P may have a finite bandwidth, which results in a differential function as P ⁻¹ (which represents the inverse of the process transfer function). In order to physically avoid excessively large signals (eg numerical implementation), a low-pass filter represented by 1 / N in FIG. 2 is added. This gives an accurate rough estimate of the disturbance torque for frequency bands below the frequency range when the low-pass filter provides for attenuation.

[0044] Note that other forms of disturbance torque estimators are possible. For example, one of the two branches may be omitted depending on the frequency band of the disturbance torque.

[0045] Figure 4a and 4b are time diagrams of the disturbance torque, stepwise function, was added thereto, Z ₁₎ above-described correcting performed have not Z direction of the reaction indicated by, and in Z ₂ shows The response including the above correction is shown. The disturbance torque is given when the time T = 0.01 seconds. This causes an error of 2 microradians around the axis extending in the X direction, as shown in FIG. 4a. This effect results in an error in the Z direction and hence in a direction substantially perpendicular to the focal plane, which is indicated by Z1 in FIG. 4b. In the absence of disturbance torque estimation and feedforward signal calculation, this error is reduced by the feedback loop. The curve Z _2, effect is shown when the disturbance torque is estimated according to the above, the correction signal is determined therewith. It can be seen that the effect of errors in the Z direction has decreased from about 200 nm to about 8 nm. This also shortens the time taken to remove the residual by adjustment. Curve Z ₂ It is noted that shows the residuals resulting from the finite approximation of the disturbance torque. This finite approximation is due to the effect that a low pass filter is incorporated into the disturbance torque estimator to make the disturbance torque estimator physically feasible. In this example, the filter cutoff frequency is set to 1000 Hz. This effect can also be seen in FIG. In this figure, the step function indicating the disturbance torque Fd is shown, but the estimated disturbance torque Fd_est slightly delayed is shown and is delayed due to the influence of the low-pass filter. Therefore, the higher the cutoff frequency of the low pass filter, the better the estimation of disturbance torque, and hence the less residual that remains in the Z position relative to the optical axis and focus position of the projection system. Become. However, in practice, the bandwidth of the low-pass filter can be set lower depending on the accuracy with which the implemented process inverse transfer function P ⁻¹ matches the actual process inverse transfer function.

[0046] The controller disturbance torque estimator and correction signal calculator are suitably implemented in any suitable form, ie, a microprocessor, microcontroller, digital signal processor is implemented in a programmable device such as any other data processing device. May be implemented in terms of software instructions and / or may be implemented in whole or in part using suitable digital and / or analog electronics. Other implementations such as optical and mechanical are also within the scope of the present invention. In the above description, the correction signal is determined to correct an error in the Z direction. However, the correction signal for the X and / or Y direction can be determined with modification if necessary.

[0047] The control system described herein can be used to control any position parameter, including stage position, velocity, acceleration, and the like. In addition, the above example relates to a substrate stage also shown as a substrate support, a wafer table, etc., but the concept described here is not limited, but includes a substrate stage and a reticle stage (reticle support and patterning). It should be understood that it can be applied to control the positional parameters of any stage including (also shown as device support). With such a stage, the same or similar considerations apply with respect to the position of the substrate stage. This is not only because the accuracy of the projection of the reticle pattern onto the target portion of the substrate is related to positioning the target portion of the substrate relative to the focal plane of the projection system, but the projection system can This is because when projecting onto the target portion, it is also related to the position of the patterning device with respect to the projection system. Thus, herein, the term stage may be interpreted as a substrate stage, a reticle stage, or any other stage or movable part in a lithographic apparatus.

[0048] Although reference herein is made in particular to the use of a lithographic apparatus in the manufacture of an IC, the lithographic apparatus described herein includes an inductive and detection pattern for an integrated optical system, a magnetic domain memory, It should be understood that it has other applications such as the manufacture of flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads and the like. In the context of such alternative applications, all use of the term “wafer” or “die” herein is considered a synonym for the more general term “substrate” or “target portion”, respectively. Those skilled in the art will appreciate that this is possible. The substrate referred to herein may be, for example, in a track (usually a tool that applies a resist layer to the substrate and develops the exposed resist), metrology tool and / or inspection tool, before or after exposure. Can be processed. Where applicable, the disclosure herein may be applied to such substrate processing tools and other substrate processing tools. Also, since the substrate can be processed multiple times, for example to produce a multi-layer IC, the term substrate as used herein already includes a plurality of processed layers. It may also refer to a substrate.

[0049] Although reference has been made in particular to the use of embodiments of the present invention in the context of optical lithography, the present invention can be used in other applications, such as transfer lithography, where the situation allows: It will be appreciated that the invention is not limited to optical lithography. In transfer lithography, the pattern produced on the substrate is defined by the topography of the patterning device. The topography of the patterning device is pressed into a layer of resist supplied to the substrate, and then electromagnetic radiation, heat, pressure, or a combination thereof is applied to cure the resist. When the resist is cured, the patterning device is removed from the resist, leaving behind a pattern.

[0050] As used herein, the terms "radiation" and "beam" include ultraviolet (UV) radiation (e.g. radiation having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm or 126 nm or near it). ), Extreme ultraviolet (EUV) radiation (e.g., radiation in the wavelength range 5-20 nm), and all types of electromagnetic radiation, including particle beams such as ion beams or electron beams.

[0051] Where the situation allows, the term "lens" refers to any of various types of optical components, including refractive optical components, reflective optical components, magneto-optical components, electromagnetic optical components, and electrostatic optical components. Means one or a combination of

[0052] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the present invention can take the form of a computer program that includes one or more machine-readable instruction sequences describing the methods disclosed above, or a data store in which such a computer program is stored. It can take the form of a medium (eg, a semiconductor storage device, a magnetic disk, or an optical disk).

[0053] The above description is intended to explain the present invention, and does not limit the present invention in any way. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

[0015] FIG. 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. [0016] FIG. 5 is a control diagram of a controller according to an embodiment of the invention. [0017] FIG. 3 is a control diagram illustrating an example of the gain scheduling matrix of FIG. [0018] FIG. 6 is a time diagram illustrating the response of a conventional control system compared to a control system according to an embodiment of the invention. [0018] FIG. 6 is a time diagram illustrating the response of a conventional control system compared to a control system according to an embodiment of the invention. [0019] FIG. 6 shows a modeled disturbance torque time diagram and disturbance estimate.

Claims (14)

A stage controller configured to control a position parameter of the stage in at least a first direction;
A disturbance torque estimator configured to estimate disturbance torque on the stage around an axis extending in a second direction substantially orthogonal to the first direction;
A signal representative of the estimated disturbance torque and a position of the stage in a third direction substantially orthogonal to the first and second directions is received, the first resulting from the disturbance torque A correction signal calculator configured to determine a feedforward correction signal for correcting a position error of the stage in a direction, wherein the feedforward correction signal is supplied to the stage;
The correction signal calculator is proportional to (a) the estimated torque around the axis extending in the second direction, (b) the position in the third direction, and (c) the mass of the stage, A control system configured to control a position parameter of the stage in a lithographic apparatus configured to determine the feedforward correction signal that is inversely proportional to the inertia of the stage relative to a second direction. The disturbance torque estimator is further configured to further estimate disturbance torque around an axis extending in the third direction;
The correction signal calculator receives (a) a signal representative of the estimated disturbance torque about the third direction and a position of the stage in the second direction; and (b) the second and third Configured to determine the estimated forward torque around the direction of and the feedforward signal in response to the position of the stage in the second and third directions;
The control system according to claim 1. The stage controller includes a gain scheduling matrix;
The correction signal calculator includes a copy of the gain scheduling matrix;
The control system according to claim 1. The stage controller comprises a feedback controller forming a closed loop control;
The control system according to claim 1. The disturbance torque estimator is
A first path extending from an error signal input of a controller for controlling rotation of the stage about an axis extending in a respective direction to an adding device and including an approximation of the process inverse transfer function of the stage When,
Extending from the controller output signal of the controller for controlling the rotation of the stage around the axis extending in the individual directions to the summing device, the output signal of the summing device provides the estimated disturbance torque A second path;
including,
The control system according to claim 4. The first and second paths each include a low pass filter;
The control system according to claim 5. The stage is configured to move with respect to a focal plane of an illumination system under the control of the control system, the first direction is substantially orthogonal to the focal plane, and the correction signal calculation A vessel is provided with a position in the second and / or third direction representing a distance in the individual direction between the center of gravity of the stage and the focal point of the focal plane;
The control system according to claim 1. A lithographic apparatus for transferring a pattern onto a substrate,
A stage for holding the substrate;
The control system according to claim 1 for controlling the position of the stage;
A lithographic apparatus comprising: Irradiating a pattern onto a substrate with the lithographic apparatus according to claim 8;
Developing the irradiated substrate;
Manufacturing a device from the developed substrate;
A device manufacturing method including: An illumination system configured to condition the radiation beam;
A patterning device support configured to support a patterning device configured to pattern the radiation beam to form a patterned radiation beam;
A support configured to support a substrate;
A projection system configured to project the patterned beam of radiation onto the substrate;
A stage controller configured to control at least one positional parameter of the support in a first direction; the support around an axis extending in a second direction substantially perpendicular to the first direction; A disturbance torque estimator configured to estimate a disturbance torque on the one and a third direction substantially orthogonal to the estimated disturbance torque and the first and second directions And a signal representing the one position of the support, and determining a feedforward correction signal for correcting the one position error of the support in the first direction due to the disturbance torque. And including a correction signal calculator, wherein the feedforward correction signal is supplied to the one of the supports, the first of the supports in at least a first direction. A control system configured to control a position parameter of
With
The correction signal calculator is proportional to (a) the estimated torque around the axis extending in the second direction, (b) the position in the third direction, and (c) the mass of the support, A lithographic apparatus configured to determine the feedforward correction signal that is inversely proportional to the inertia of the support relative to the second direction. A stage controller configured to control at least one other positional parameter of the support in the first direction;
A disturbance torque estimator configured to estimate a disturbance torque on the other one of the supports around the second direction;
Configured to receive the estimated disturbance torque and the other one position of the support in the third direction, and the other of the support in the first direction due to the disturbance torque. A correction signal calculator configured to determine a feedforward correction signal for correcting one position error, wherein the feedforward correction signal is supplied to the other one of the supports;
And further comprising another control system configured to control the other one position parameter of the support.
A lithographic apparatus according to claim 10. The disturbance torque estimator is further configured to further estimate disturbance torque around an axis extending in the third direction;
The correction signal calculator (a) receives a signal representative of the estimated disturbance torque about the third direction and the one position of the support in the second direction; and (b) the second Configured to determine the estimated disturbance torque around the second and third directions and the feedforward correction signal in response to the one position of the support in the second and third directions;
A lithographic apparatus according to claim 10. The stage controller includes a gain scheduling matrix;
The correction signal calculator includes a copy of the gain scheduling matrix;
A lithographic apparatus according to claim 1 0. Adjusting the radiation beam;
Patterning the radiation beam to form a patterned radiation beam using a patterning device supported by a patterning device support;
Projecting the patterned beam of radiation onto a substrate supported by a substrate support;
A stage controller configured to control at least one positional parameter of the support in a first direction; the support around an axis extending in a second direction substantially perpendicular to the first direction; A disturbance torque estimator configured to estimate a disturbance torque on the one of the first and the estimated disturbance torque in a third direction substantially orthogonal to the first and second directions And a signal representing the one position of the support, and determining a feedforward correction signal for correcting the one position error of the support in the first direction due to the disturbance torque. And using the control system comprising a correction signal calculator, wherein the feedforward correction signal is supplied to the one of the supports, the one of the supports. And controlling the position parameter,
Including
Controlling the one positional parameter of the support comprises: (a) the estimated torque around the axis extending in the second direction; (b) the position in the third direction; and (c) the Determining the feedforward correction signal proportional to the mass of the support and inversely proportional to the inertia of the support relative to the second direction;
Device manufacturing method.

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